טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentGeller Arie
SubjectThe Use of Non-Potable Water for Earth Work and Construction
of Granular Pavement Layers in Highways
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Ilan Ishai
Dr. Guy Levy
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Processing of soil and paving materials requires water. In Israel, potable water is used for this purpose. An alternative to the use of expensive potable water could be the use of much less expensive treated effluent water (used extensively in agriculture) and saline water from local aquifers. However, no knowledge exists with respect to the possible impacts of nonpotable water on the geomechanical properties of soils. An indepth study of the engineering and environmental impacts of using  non-potable water for the processing of earthworks and paving materials is therefore needed.

Goals of this research

The main goal of this study was to examine the effects of using non-potable water on geomechanical properties of soils and paving materials. The specific objectives of the study were:

a.       Investigation of the impact of non-potable water on the engineering and physiochemical properties of soils and paving materials in comparison with potable water.

b.      Quantification of long term effects on soils and paving materials resulting from the use of non-potable water for their processing.

c.       Testing of the impact of using nonpotable water in the processing of soils and paving materials on the environment.

Research methods

The following water were studied: potable water; desalinated water; secondary treated effluents,; tertiary treated effluents; saline water ; seawater; de-ionized water; and water that has been synthesized to different levels of salinity sodicity.

The soils and materials studied included nine soils varying in texture, a sand dune, crushed subgrade materials, subbase materials and crushed construction waste from two different waste collection sites.

The following tests were performed: moisture-density systems, CBR-moisture systems, swelling rate, swelling pressure, unconfined compressive strength, direct shear, spatial shear, interlayer slippage, Atterberg limits and permeability, and the strength of asphaltic concrete.  The structure of the study was not fully factorial.

Principal findings and conclusions

-          The various nonpotable water types used did not have short- and long-term effects on  the geomechanical properties of the soils andgranular paving materials studied compared to using potable water. Only in the light-textured Loam, certain weakening in the strength parameters were noted when secondary effluent water was used. Possibly, the presence of organic materials in the effluents led to some "lubricating" phenomenon that worked against the interior cohesion of the Loess. However, this weakening phenomenon disappeared as the clay content of the Loess soil increases.

 

-          The permeability tests showed  that no passage of processed water or other water into the soil under roads based on clay, Loess and sandy Hamra soils, occured, suggesting that use of nonpotable water  does not pause a risk to soil or groundwater quality.

-          No risk to the stability of bituminous layers in roadways and runways resulting from salt  migration to the surface from granular layers processed with effluents or saline water, was noted.

Given the findings of this study, it may be concluded that there is no impediment to the use of treated effluent water (especially tertiary treated effluents) or saline water (<2500 mg/L of chloride) for earthworks and paving.